import-trace: alias-based (importer) registry

This change implements a generic registry in order to clean up import-trace's
code - it's possible (and reasonable) to use the registry for pruners as well.
Importer now extends AliasedRegisterable; all importers have been adapted
to suit the interface/abstract methods.
Each AliasedRegisterable should have at least one alias (the class' name
is a sensible choice) but can have several. The first specified alias is
the class' prime alias which can be used e.g. to list all registered objects.

Change-Id: If6daa34edce35a3b0194e4ba67ed3b44b74a49b0

tools/import-trace/Importer.hpp

@@ -11,8 +11,9 @@
 #include "util/Database.hpp"
 #include "util/MemoryMap.hpp"
 #include "comm/TracePlugin.pb.h"
+#include "util/AliasedRegisterable.hpp"
 
-class Importer {
+class Importer : public fail::AliasedRegisterable {
 public:
 	typedef unsigned instruction_count_t; //!< not big enough for some benchmarks
 	struct margin_info_t { instruction_count_t dyninstr; fail::guest_address_t ip; fail::simtime_t time; };